The peptide pools contain HLA class I or II restriced epitopes from human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), influenza virus (FLU) and/or from tetanus toxin. Most people have already been exposed to these antigens and have the corresponding CD8+ and CD4+ memory T-cells. This means that, unlike traditional reagents such as PHA, PMA, or ionomycin, CEF and CEFT pools are ideally suited for use as specific positive controls for a T-cell based assay (such as intracellular flow cytometry analysis or ELISPOT assays).